Perhaps that explains why Harrington leaped 6 feet, 4 inches as a sophomore in the high jump, which ranked No. 1 in Florida at the time.
And perhaps that explains why Harrington has started since his freshman year on his varsity basketball team, routinely soaring over the rim for tip-dunks -- even though he is only 5-foot-9.
That athleticism is what no doubt attracted Cougars head coach Mike Leach and his staff to Harrington, who committed to Washington State in May.
It doesn't hurt that Harrington's school, St. Petersburg Northeast, runs Washington State's Air Raid offense.
"I feel like I'm a perfect fit in (the Air Raid) offense," said Harrington, a 174-pound senior who can bench press 245. "It's very explosive."
Explosive, however is not how anyone would describe the current Northeast offense.
The 0-4 Vikings have yet to score a point this season – but there are extenuating circumstances.
Right before the start of fall camp, the Vikings' offensive coordinator left for another school, St. Petersburg Admiral Farragut.
Then the floodgates opened, and six starters, mostly on offense, transferred out, including quarterback Ryan Davis, who threw for 2,120 yards and 19 TDs last season. Davis, who is now at St. Petersburg Lakewood, has numerous Division I scholarship offers as an "athlete."
The result of the loss of Davis and the others is that Northeast has been outscored 127-0 so far this season.
Amazingly, though, Harrington has retained an exceptionally positive attitude.
"I think we are going to win our next four in a row," said Harrington told Cougfan.com in a recent interview. The Vikings' next game is against Pinellas Park on Friday. "It's been kind of bad, but we still have time to turn it around."
Harrington has been used all over the field this season -- quarterback, running back, wide receiver, cornerback and safety. He missed two games with shin splints but came back and posted a pair of 100-yard rushing games.
"Keith has played well, but we've struggled," Northeast Coach Mike Jalazo said. "We've played five different kids at quarterback. We just haven't been able to throw the ball.
"We've been most effective when we put Keith at quarterback and let him create. But he's not a quarterback."
Jalazo said the Vikings have finally settled on senior quarterback Jeff D'Alvia, and that should help Harrington.
"Keith is stronger than last year and faster than last year," Jalazo said. "He's also smart. But the best part is his passion for the game. I've coached guys who are now in the NFL, and Keith has more passion and enthusiasm for football than those guys."
Jalazo said NFL linebacker Colin McCarthy is one of his former players that reminds him of Harrington in that regard. But even McCarthy doesn't have Harrington's enthusiasm, according to Jalazo.
As for his role at Washington State, Harrington said the Cougars want him as a slot receiver, where he can use his leaping ability and 4.47 speed to catch passes and score touchdowns.
"I like to get into space and make things happen," said Harrington, whose father, Keith Sr., was a football star at St. Petersburg High but never played in college.
Harrington Jr. grew up playing basketball and didn't try out for football until his freshman year.
He quit track after he injured his heel as a sophomore, but he still plays basketball, averaging 16 points – mostly on put-backs – and eight rebounds as a high-leaping but undersized forward.
He hasn't met quarterback Peyton Bender, the Cougars' other 2014 recruit from Florida. But they have exchanged messages on Twitter.
"I just told him that we're family now," Harrington said. "I told him that if he needed anything, I'm here."
Harrington, who has a 3.2 grade-point average, aspires to be a college coach one day.
In the meantime, though, Harrington is focused on turning around the Vikings. Last season, he had 1,350 yards from scrimmage for a 7-3 team.
But the mass exodus at Northeast has so far damaged Harrington's senior season.
Once the season ends, Harrington plans on visiting Washington State for the first time.
Harrington, who considers his commitment to the Cougars "solid," has turned down Arizona, Iowa State, Indiana, Wake Forest, FIU and Marshall to hitch his wagon to the Cougars and their creative coach.
"(Leach) is very cool," Harrington said. "He is very smart on the field with his offense and calling plays. I really want to play for him."
About the author: Based in Miami, Walter Villa is a free-lance writer who has written for The New York Times, Los Angeles Times, ESPN.com, Baseball America, Sports Illustrated.com and many more. He also served as an assistant sports editor at The Miami Herald for 15 years.
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